Unraveling the Harmonious Coexistence of Ruthenium States on a Self‐Standing Electrode for Enhanced Hydrogen Evolution Reaction

The development of cost‐effective, highly efficient, and durable electrocatalysts has been a paramount pursuit for advancing the hydrogen evolution reaction (HER). Herein, a simplified synthesis protocol was designed to achieve a self‐standing electrode, composed of activated carbon paper embedded with Ru single‐atom catalysts and Ru nanoclusters (ACP/Ru SAC+C ) via acid activation, immersion, and high‐temperature pyrolysis. Ab initio molecular dynamics (AIMD) calculations are employed to gain a more profound understanding of the impact of acid activation on carbon paper. Furthermore, the coexistence states of the Ru atoms are confirmed via aberration‐corrected scanning transmission electron microscopy (AC‐STEM), X‐ray photoelectron spectroscopy (XPS), and X‐ray absorption spectroscopy (XAS). Experimental measurements and theoretical calculations reveal that introducing a Ru single‐atom site adjacent to the Ru nanoclusters induces a synergistic effect, tuning the electronic structure and thereby significantly enhancing their catalytic performance. Notably, the ACP/Ru SAC+C exhibits a remarkable turnover frequency (TOF) of 18 s −1 and an exceptional mass activity (MA) of 2.2 A mg −1 , surpassing the performance of conventional Pt electrodes. The self‐standing electrode, featuring harmoniously coexisting Ru states, stands out as a prospective choice for advancing HER catalysts, enhancing energy efficiency, productivity, and selectivity.